Showing posts with label Evolution. Show all posts
Showing posts with label Evolution. Show all posts

Monday, November 5, 2012

Special Edition: November 6, 2012 - Evolution and Gene Expression

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November 6, 2012 Evolution and Gene Expression


Suggested Reading

Prior to accepting the daily challenge, read the following articles.

Evolution has its base in genetics. All variation starts with mutation. The addition, deletion or change in the nucleotide sequence of a coding region can result in protein changes. Any mutation, if it has an expressed effect, then becomes subject to the mechanism of Natural Selection.

A great example of this nucleotide alteration is seen in Sickle Cell Anemia. A change in one nucleotide causes a conformational change in the β-hemoglobin chain, which causes the entire expression of the disease (the altered hemoglobin molecule is known as HbS). Review the β-hemoglobin gene sequence and see how just one point-mutation can have such a strong effect. Also note, this is a change in the third nucleotide of a codon.

Optional Challenge

Your task today is to discuss the relationship DNA changes and Gene Expression has with evolution. Sit with the concept for a moment, and come up with a coherent discussion. Feel free to use models such as Sickle Cell Anemia. Remember, this alteration in gene expression sets up the diversity of the population. Natural Selection then acts on the new phenotype.
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Friday, October 26, 2012

Daily Newsltter: October 26, 2012 - Mendel, Meiosis and Evolution

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October 26, 2012

Mendel, Meiosis and Evolution


With meiosis we see the mechanism of inheritance first hinted at by Mendel. Gregor Mendel discussed how each person has two "copies" of the information that gives rise to a physical trait (genes), and that there were variations in that information which gave rise to different expressions of these traits (alleles).

Mendel's work gave biologists an understanding of inheritence, and an understanding of chromosomes and nuclear division helps to understand Mendel's inheritence model and the variations of that model. With cross-over in Prophase I, and the random seperation of homologs in Anaphase II, we can see the recombination of parental genes that result in genetically unique gametes (sperm and egg). This results in genetically unique individuals each generation.

Diversity is one of the greatest advantages of sexual reproduction. While >99% of our genes are held in common within a species, there is sufficent genetic variation to allow provide a species with a broad adaptaion range. Remember, the goal of evolution and survival resides not in the individual, but in the population. Those with genetic, metabolic, or physiological advantage will have a greater chance to leave offspring; thus the species survives and thrives.

In class, I mentioned that when you get to the core of biology, it is ultimately all about sex. Not the physical act, but the concept. The recombination of genes allows for diversity. Some organisms spend most of their life in haploid, or non-sexual reproductive states. They only expend the energy for sexual reproduction when they need to insure the survival of their offspring.

Daily Challenge


Today, you are to reflect upon what you have learned so far regarding metabolism, Mendelian inheritence, and meiosis. Build a picture of evolution based upon the need for a diverse population. Use an example to help illustrate the need for diversity. As a starting point, look to endangered species (why is it a problem when you have few individuals left?) or look at what happens when you have genetically similar trees struck by disease (Pine Bark Beetle infestations).
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Video Challenge


Today, I'm going to give you a video challenge. Below is a link to a video about animal genitalia (penises to be percise). The video is informative, but at times very vulgar (so be warned). The video's narrator makes some interesting, and humorous, comments about evolution.

What you are to do is reflect upon the views of evolution discussed. What insights can you glean from the narrator and the topic, and what errors are made (even jokingly) about evolution.

The World's Most Terrifying Penises: The Echidna

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Friday, September 28, 2012

Daily Newsletter: September 28, 2012 - Metabolic Evolution & Scientific Articles

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Today you are going to look over a scientific article dealing with the evolution of metabolic processes. This is the first scientific article assigned, so I want to spend a little time going over how to read a scientific article.
One of the biggest struggles students have in science is reading scientific articles. These articles are dense, meaning they convey a great deal of information quickly. They are intended for experts, who have an understanding of the background, procedures and protocols. As a result, they are an obstacle when someone new to the field tries to figure out what the authors are saying in the paper.
Most people when they come to a scientific article start with the first line and then plow their way through. Novices become quickly overcome by the language, protocols and jargon, and just get frustrated. Experts rarely read the article from start to finish, but instead skip around. They use the break down of the article to focus their attention on what interests them.
All scientific articles start with an abstract. This is a summation of the paper, but be warned, this summation can be misleading. The purpose of the abstract is to provide a brief rundown of the paper so that people who are looking for an background or protocols can determine if the paper will be of use to them. WARNING: the abstract is for experts, not novices. More than one student has been burned by reading just the abstract and thinking they understood the paper.
While this may be heresy to some, skip the abstract. Don't read the abstract when you'rer assigned a paper. Remember, it is helpful to some one searching through articles. If you are assigned a paper by a teacher, skip the abstract. Instead, go right to the paper's introduction.
Scientific articles are generally broken down into section, with the most common being an introduction, methods, results and conclusion(discussion)*. The introduction holds the background for the paper, and generally includes why the author thinks the study is important. You can usually find the authors hypothesis and assumptions (research logic) here as well.
When you start reading the introduction, do not have a pencil or highlighter in hand. Just do a read through. If you don't understand something, skip it and go on. Just make it through once. On a note pad, write your first impressions. What stood out to you? Start a second read through, but this time have a highlighter, pen or pencil. Mark statements (does not have to be a full sentence) that you think are important. Write down any notes. Ultimately, your looking for a few things in the introduction:
  1. Why does the author think this topic is important?
  2. What has led to this current research?
  3. What is the author's hypothesis?
  4. New terms:
    • Since your new to scientific papers, many of the terms will be new.
    • To start, pick three that seem important to what the author is doing.
    • Look them up and make a note of their definitions somewhere on your copy of the article. (a few words will do)
On your note pad, answer the questions above and make notes.
The METHODsection is one of the hardest to read for a novice, because the whole thing is filled with information on the exact procedures used. Unfortunately, this means you need to have background knowledge on how to do most of these procedures. But this is where we start to learn new techniques. On your first time through, just skim over the method section, but you need to come back to it (Just not immediately)
What to look for in the methods:
This ultimately depends on why you're reading the paper. Are you looking for a method? Are you trying to find an experimental protocol? Or are you trying to figure out how the author got their results? So the questions you ask could change depending upon your goals. The paper you have today has a non-standard arrangement, and the experimental protocol section is minimized (it is actually fleshed out in other sections). Generally though, you want to look to answer the following question:
  1. How did the author set up the experiment?
  • Did they use models systems? (Did they go to a location or did they attempt to replicate the system?)
  • What controld did they use?
  • How many replicates did they have?
  • What experimental methods did they use?
Remember: Do not get bogged down trying to figure out their methods. It is OK if you can not fully answer the questions above. For your notes, pick one procedure that they used and look it up. Write down a one or two sentence description of what the procedure is used for and/or how it is done. It is important to remember that we learn procedures from reading scientific papers.
You should be able to trace the RESULTS back to particular methods used. A good author will provide you a story that leads from methods to results, and finally to a discussion about their conclusions. Results sections normally provide just the FACTS (evidence) that was generated from the methods. As the reader, you are looking to see if the results provide evidence supporting or refuting the authors hypothesis. Your also looking to see what the data says to you. Do the results tell you the same thing they "told" the author? i.e., the results will inform (be the foundation for) the author's conclusions. Based on the same evidence, do you reach the same conclusion? Why or why not? *NOTE: The article today combines results and discussions.
Again, you need to have a good background in the methods to understand and interpret results. So, your goal as a novice is to begin looking at the data to gain an understanding of what the data represents. This is about learning to read graphs and charts. Good authors will lead their reader through the data, but authors have different skills at conveying their data. For the paper today, take one graph, and see if you can figure out all that it is trying to convey. Read the results section, and find where the author discusses the graph. What are they trying to say? *NOTE: For today's paper, explain the results shown in Figure 1.
In the Discussion/Conclusion of the paper, the author attempts to tie together their results and present a logical case supporting their hypothesis. The emphasis here is on LOGICAL. How does the author support the hypothsis? What statements are made to demonstrate how the results support the hypothesis?
For the paper today, find a statement that you think shows where the author demonstrates the data supporting the hypothesis. Also, does the author address future directions for the research? Do they make specific claims?

Reference

Huber, C., Kraus, F., Hanzlik, M., Eisenreich, W. and Wächtershäuser, G. (2012), Elements of Metabolic Evolution. Chem. Eur. J., 18: 2063–2080. doi: 10.1002/chem.201102914
Go to the GSU Library Homepage. Above the search box on the left, you will see a series of tabs. Click on the Journal tab. Type the word chemistry, and click GO. This will bring up a series of Chemistry Journals. You are looking for Chemistry : a European journal. Click on the Find It @ GSU button. You will need to sign-in if you are off campus; follow the sign-in proceedure.
You will then see a series of links that show the access GSU has to different versions. Click on the Full Text Online link. This will take you to the paper. You will have the option to open the paper as a PDF. This is the best way to get a copy to print or save. Open the paper and start to read and take notes.

Daily Challenge

Read the article listed above. In the forum, write about the article. The specific information you need to add includes:
  1. Why does the author think this topic is important?
  2. What has led to this current research?
  3. What is the author's hypothesis?
  4. Three new terms.
  5. How did the author set up the experiment?
  6. New methods/protocolsa
  7. Analysis of Figure 1.
  8. How does the author link data to support hypothesis (conclusion)?
  9. One specific claim or future direction for research.
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Optional Challenge

Review of Lecture on September 28, 2012.
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Friday, September 14, 2012

Daily Newsletter: September 14, 2012 - Evolution Friday

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September 14, 2012 Evolution Friday


The evolution of the cell, especially the development from prokaryote to eukaryote, is an important topic as it demonstrates core differences between living organisms. Archaea, Bacteria, and Eukarya are dramatically different from each other, but even within these domains, there are vast differences in cell types. When studying the development of cellular differences and structures, and thus studying the evolution of cells, biologists often look toward existent organisms that do not fit the typical cellular model. Anomalous structures give us insight into possible evolutionary steps.Symbiodium symbiosis with Jellyfish
For example, the genus Symbiodinium is an algae of the phyllum Dinoflagellata. These algae are known to live inside the cells of cnidarians (corals and jellyfish). Within the cell, they algae will deliver photosynthetic products to the cnidarians. Sound familar? How does this cell "know" to become symbiotic? Are there signals between the two cells? Does this mimic the entry of a Cyanobacteria into a cell where it became the chloroplast?
Then there is the bacterial phyllum Planctomycetes which researchers suspect is the "missing-link" between prokaryotic and eukaryotic cells, i.e., the development of a nucleus. Beyond membrane alterations, this is a bacteria that reproduces by budding (the daughter cell has a reduced cytoplasm). Other bacteria reproduce by binary fission, which results in two daughter cells with equal cytoplasm.Bdellovibrio Life Cycle
The bacterium Bdellovibrio is of interest in that it is a predator of other bacteria. This organism hunts other bacteria, enters their cell wall, then devours them. This is a very unusual characteristic. Not only in the recognition of prey, but in the entire life cycle. This is a complexity that we do not see in other bacterial groups.



Daily Challenge

Review the following diagram showing proposed steps in the evolution of the eukaryotic cell.
Evolution of Eukaryotic Cell
In your own words, discuss the origin of the eukaryotic cell. Using the examples above, and any others you find, how can we provide evidence of these evolutionary steps or stages. Some claim that the Archaea are the ancestors of the Eukarya, but if so, why are there so many differences, espeically when it comes to phospholipids? How easy would it be to change the phospholipids a cell uses?

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Wednesday, September 12, 2012

Daily Newsletter: September 7, 2012 - Evolution Friday

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September 7, 2012 Evolution Friday


As with most scientific thought, the theory of evolution has been fefined since it's first conception. This occurs as we learn more about organisms. For instance, Darwin did not have a valid hypothesis regarding how inheritence of characteristics occurred. He knew that we inherited characteristics from our parents (phenotypes), but not how this occurred. In his own words "[t]he laws governing inheritance are quite unknown...."1 This is not unusual. We may see a pattern in nature, but we are not yet be able to explain it. The observed pattern is a model that we can start with, but ultimately, we want to find a way of understanding the pattern.

In 1866, Gregor Mendel published his work on plant hybridization, which included his mathematical descriptions of inheritence. Historians have shown that Darwin was not aware of this work, and it did not have a significant impact at the time. His work was 'rediscovered' during the 1890's, and a publication by Hugo de Vries of his own work and subsequent credit to Mendel's initial work led people to being looking at the science we know know as genetics.

There was actually a vigous debate between Darwinians and Mendelians as to which system best represented evolution. This debate would continue for years. The work of Sir Ronald Aylmer Fisher, a British biologist and statistician, would be instrumental in combining the work of Darwin and Mendel, and their intellectual descendents, into a new system. Sir Fisher was also one of the pioneers of population genetics, a field of study instrumental in modern evolutionary thought. His book, The Genetical Theory of Natural Selection, published in 1930, is considered one of the foundations of modern evolutionary thought. (NOTE: There were other's working at this time on this issue, including Ernst Mayer, Theodosius Dobzhansky, and George Gaylord Simpson. Fisher is discussed in detail here as his work became a turning point in the discussion of evolution).
So, what is this modern evolutionary view?
Here are a few brief articles to look at:

Daily Challenge

Read the articles above, and discuss the formation and refinement of scientific theories, specifically as it relates to evolution. One a hypothesis becomes a theory, is it set in stone? If we learn something new, does it over turn a theory, or could it explain something we previously didn't know? Is debate among experts useful in refining theories? Are we still refining the theory of evolution?
Additonally, what are the "main" points (concepts) of the modern theory of evolution?
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Reference

The reference below is linked to an online copy of the book.  While not required, it is a book all biology students are encouraged to read at some point.
1. Darwin, C. R. 1859. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. [1st edition]

Daily Newsletter: August 31, 2012 - Evolution Friday

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August 31, 2012 Evolution


***NOTE: This Newsletter is coming out early.
Remember that as scientists we build models to help us understand how the world works, and to provide the ability to predict and control natural phenomena. Evolutionary theory is no different. The model we create regarding evolution allows us to look at the diversity and interrelation of living organisms, understand strong connections between organisms, and even understand what happens when population sizes get low (endangered species). Our modern model of evolution can be stated at a simple level as the changes in phenotypic frequencies within a population through time. Let's analyze that statement:
  1. Phenotype: This is the physical, expressed form of an organism.
  2. Population: A group of individuals of the same species inhabiting the same time and space (habitat).
  3. Unless there is an identical twin, each organism in a population is phenotypically unique (diversity).
  4. Even with this diversity, there is a range of expressed phenotypes; or a phenotypic ratio.
  5. Evolution looks at this phenotypic ratio over time to see if there are changes.
  6. Another way to look at this right now is to say that we are looking at the PREVALENCE of a given phenotype (characteristic) over time.
The idea that natural selection can affect phenotypic frequencies is a central model used in biology. It informs our hypotheses and conclusion.
Brush up on evolution by reviewing the material found at Evolution 101 and the Evolution FAQ.

Once you have finished reviewing these sites, read the following article:


Daily Challenge: Evolution

This challenge has two components. First I would like you to discuss the modern concept of evolution in your own words by answering the question: What is Evolution? Second, I would like you to read the above article and discuss the following question: How does evolutionary theory inform the conclusion to this article? Another way to put this, how does evolutionary theory inform the author's conclusion about the stability of grasslands.
Evolution Discussion Forum